NASA has been without its own launch vehicle since the retirement of the Space Shuttle in 2011. That won’t be the case for much longer. The agency hopes to begin flying the Space Launch System (SLS) in 2020 without a crew, and manned missions to deep space could start as soon as 2023. It’s actually looking more likely NASA will be able to stick to that schedule, but with a less powerful version of the rocket. According to NASA administrator Robert Lightfoot, NASA now plans to use the Interim Cryogenic Propulsion Stage for early manned flights.
The SLS is an expendable heavy lift vehicle, which will make each launch more expensive, but maximizes the cargo capacity. It includes a pair of solid rocket boosters, a first stage, and second stage. NASA plans several upgrades to the rocket, and the second stage is where the changes are happening. Initially, the Block 1 configuration with the Interim Cryogenic Propulsion Stage (ICPS) was only on the table for the first unmanned launch, but progress has been slow on readying the more powerful upper stage (Block 1B and Block 2). Luckily, NASA now has an alternative.
As part of the 2018 budget passed by Congress several weeks ago, NASA got $350 million to build a new mobile launch tower at Kennedy Space Center. There’s already one tower for moving and launching the SLS, but it would need a complete rebuild down the line to accommodate the Block 1B and Block 2 variants of the rocket. With the extra funding, NASA plans to start building a second tower for Block 1B and Block 2 while it continues to use the existing tower for more Block 1 launches. This should allow NASA to fly the SLS Block 1 configuration with ICPS several more times before switching to the more powerful upper stage, which will increase lift capacity by about 50 percent.
This funding increase probably has NASA officials breathing a sigh of relief. The agency has been struggling to complete designs for the 18-meter upper stage, which was supposed to have four RL-10 engines. However, NASA has put the word out that it’s interested in cheaper alternatives. It may still be four or five years before the Block 1B upper stage is complete, and that would be a close call for the planned mission timeline.
The current thinking is NASA will use the Block 1 configuration for an additional two or three launches. That covers the unmanned test flight in 2020 as well as the first manned mission in 2023. That mission is supposed to take astronauts on an orbit around the moon. NASA may need to make some tweaks to the plan to compensate for the less powerful launch vehicle, though.